The present invention relates to air-bearing sliders used in disk drives. In particular, it relates to air-bearing sliders that are negatively pitched relative to the disk.
Disk drives are data storage devices that are routinely used with computers and other data processors. In a disk drive, the transducer element, commonly referred to as the head, reads and/or writes data from a spinning data-storage medium, or disk. The head is typically formed as part of an air bearing slider that is fixed to a suspension. The suspension helps to damp vibrations and keep the slider and its head steady. With reference to FIG. 1, the suspension 230 is attached to an actuator arm 210. The entire head-carrying assembly 200 is deployed to a desired radial position over the disk 100. The slider and head are not shown in FIG. 1 because they would typically be disposed on the disk-facing side of the suspension 230 near the distal end 204 of the head-carrying assembly 200. With the disk 100 spinning in the direction indicated by 120, a flow 125 is induced adjacent to the disk 100.
One of the challenges of disk-drive design is to maintain the head at a very precise location that is preferably a very small fixed distance above the disk. Variations in the height of the head from the disk increase the probability of read/write errors. An exceptional design would hold the head at a fixed height above the disk over a large range of conditions.
Modern disk-drive design attempts to achieve this goal in part by tailoring the details of the slider. As the disk spins, the air adjacent to the disk is induced to rotate substantially with the disk, as is shown in FIG. 1. Only the flow deflected by the head-carrying assembly 200 and the flow near the outside diameter of the disk 100 deviate much from the substantially solid-body rotation of the flow. The slider flies in the induced flow. The aerodynamic forces generated on the slider are balanced by the suspension to which the slider is attached. A balance between the design aerodynamic forces on the slider and the restoring elastic forces imposed by the suspension is required to maintain the slider, and hence the head, at the desired fly height. However, as the head-to-disk spacing reduces further in the near future, the slider may contact with disk asperities or the disk surface itself. In such circumstances the force balance is more complex and must include the aerodynamics forces generated on the slider, the elastic forces imposed on the slider by the suspension, and the contact and frictional forces imposed on the slider by the disk contacts and friction. In addition, during data accessing, the slider is quickly moved radially by the action of the actuator. This imposes a radial inertial force to the slider and is balanced by forces generated by changing the flying attitude of the slider. To design a slider that minimizes this data accessing fly height variation is challenging.
All currently used sliders are designed so that in the induced flow, the leading portion of the slider is lifted away from the disk slightly more than the trailing portion of the slider. This type of slider has positive pitch. In a slider with positive pitch, the head is located in the trailing portion of the slider, i.e., in that portion of the slider that is closest to the disk. For disk drives with conventional flow, wiring is simplified with the location of the head in the trailing portion of the slider.
The current invention explores a new paradigm for the design of sliders used in disk drives. Rather than continuing to design sliders with positive pitch, the current invention includes sliders that are designed to fly with negative pitch. Such designs are typified by having at least one point in the leading portion of the slider closer to the disk than any point in the trailing portion of the slider when the slider is flying in the flow induced by the spinning disk.
Another way to imagine a negatively pitched slider is to consider a ray from a first point in the trailing portion of the slider through a second point in the leading portion of the slider. The first and second points are chosen such that in the absence of flow, the ray would be parallel to the disk, but in the presence of flow, the ray intersects the plane of the disk surface. This occurs if the flow tilts or pitches the trailing portion further from the disk than the leading portion.
Tests indicate unexpected benefits from the use of the negatively pitched slider. The negatively pitched slider has reduced fly height sensitivity to ambient pressure variations and to radial location over the disk. In addition, during data accessing, the negatively pitched slider experiences a reduced drop in fly height relative to a positively pitched slider. Therefore, flying a slider such that a point on the slider closest to the disk is located on the leading portion of the slider is useful for achieving reduced head altitude sensitivity to ambient pressure and radial position, and reduced fly height variation during data accessing.
Because the head is usually located near the point of closest approach to the spinning disk, most embodiments of a negatively pitched slider will have the head coupled to a head pad in the leading portion of the slider. Although having the head in the leading portion of the slider complicates the wiring in disk drives with conventional flow, it simplifies the wiring in reverse-flow disk drives. Large reductions in head vibration and fly height variation have been observed when a negatively pitched slider is used in combination with reverse flow.
Additional features and advantages of the invention will be set forth in part in the description that follows, and in part will be obvious from the description, or may be learned by practice of the invention. Various embodiments of the invention do not necessarily include all of the stated features or achieve all of the stated advantages.